Alloy 254 (UNS S31254)

Description:

Alloy 254 is a high alloy austenitic stainless steel which is supplied in the hot worked and annealed condition. Significant additions of Mo, Ni and Cu gives this alloy a good resistance to pitting and crevice corrosion, especially in environments containing halide ions e.g. chloride, bromide and fluoride solutions. It is therefore widely used in applications in brackish water, seawater, pulp mill bleach plants and other chloride process streams, where it can be a cost-effective alternative to more expensive nickel and titanium alloys in such environments.

The high alloy additions ensure that it has a strength nearly twice that of 3xx austenitic stainless steels. It retains excellent ductility and toughness at both elevated and sub-zero temperatures. It can generally be formed and welded in the same way as other 3xx alloys, but the high work hardening rate means that machining may require slower speeds / more power.

Key Features:

  • High alloy additions means that it has a Pitting Resistance Equivalent number (PREN) of ≥42
  • Excellent corrosion resistance in seawater and concentrated halide environments
  • High resistance to stress corrosion cracking
  • Resistant to crevice corrosion in seawater
  • Good resistance to erosion corrosion
  • Excellent ductility and impact strength at both ambient and sub-zero temperatures
  • Low magnetic permeability

Applications:

  • Process industry equipment in urea production, organic & fatty acids, high halide concentration environments
  • Oil & Gas industry heat exchangers, piping, valves and pumps
  • Power generation for flue gas desulphurisation (FGD) applications
  • Marine and shipbuilding piping, pumps, valves and heat exchangers
  • Water treatment facilities, such as piping and condensers in desalination plant
  • Pulp and paper processing for bleaching plant, vats, drums, press rolls and piping

Chemical Composition:

Cr Ni Mo Co Nb (+Ta) Ti V W Cu C Mn N Si P S Fe Al
Min 19.50 17.50 6.00 0.50 0.18
Max 20.50 18.50 6.50 1.00 0.02 1.00 0.22 0.80 0.03 0.01 Bal

Mechanical Properties:

0.2% Proof Stress 300 N/mm2 43.5ksi
Tensile Strength 650 N/mm2 94.25ksi
Elongation, 5.65√S0 and 4D 35%
Reduction of Area 50%
Hardness (Brinell) <270
Impact Strength (Room Temp)
Impact Strength (-60degC)

Notes:

  1. Testing shall be carried out in accordance with ASTM A370 or EN ISO 6892-1 (tensile), EN ISO 6506-1 (hardness)
  2. Minimum properties quoted (tested at room temperature in a longitudinal direction)
  3. Testing performed on each melt of material per heat treatment batch
  4. Additional tests routinely undertaken:
  5. ASTM G48A corrosion test (at 50°C) No pitting (at 20x magnification) and < 4.0g/m2 weight loss

Physical Properties:

Density (Kg/m3) 8000
Magnetic Permeability (20°C) <1.05
Young’s Modulus (kN/mm2) 200
Specific Electrical Resistance, 20°C (Ω-m) 0.85
Mean coefficient of thermal expansion, 20-100°C (m/m/degC) 16.5
Specific Heat, 20°C (J/kg.K) 500
Thermal conductivity, 20°C (W/m.K) 13.5

Downloads

Datasheet - S-Alloy 254

Datasheet - S-Alloy 254